This invention relates generally to gas turbine combustion technology and, more specifically, to a flow sleeve and combustor liner arrangement configured to redirect cooling air toward a particular target area.
In a gas turbine combustion system, the combustion chamber casing contains a liner which is typically constructed in a generally cylindrical configuration, with a closed forward end and an open aft end. Fuel is ordinarily introduced into the liner via one or more fuel nozzles at the closed end, while combustion air is admitted through circular rows of apertures or air mixing holes spaced axially along the liner. These gas turbine combustion liners usually operate at extremely high temperatures and depend to a large extent on incoming compressor air for cooling purposes. More specifically, combustor liners are typically impingement cooled by flowing compressor discharge air through a series of cooling apertures provided in a flow sleeve surrounding the liner.
In some instances, cooling inserts or thimbles have been located in the flow sleeve cooling apertures to bring the cooling air jets into close proximity with the liner surface, or even more specifically, with known hot spots and welds. The inwardly-projecting thimbles create undesirable pressure drop, however, in the flow of combustion air along the radial space between the flow sleeve and the liner.
There remains a need, therefore, for a technique for cooling localized hot spots and/or welds that provides increased durability but less pressure drop, and without negatively impacting cooling efficiency.